An ultrasound diagnostic device is used in various medical fields. The ultrasound diagnostic device is adapted to transmit ultrasound signals to organs and acquire an ultrasound image by detecting the ultrasound signals that reflect from the organs. When the ultrasound signals are transmitted to the organs, the reflection and scattering of the ultrasound signals occur at the same time, thus generating a speckle noise. The speckle noise degrades not only the ultrasound image quality but also the accuracy of displaying important parts such as the boundary between a target object and a background. Also, the speckle noise makes it difficult to analyze the ultrasound image and to distinguish different types of organs from the ultrasound image.
In order to resolve the above-identified problems, a method for removing the speckle noise has been sought and researched in the art. Currently, the most widely used method for removing the speckle noise is to apply a heat equation. According to this method, the pixels of an ultrasound image are segmented into a plurality of areas wherein an appropriate Gaussian filtering for each area is carried out, thereby removing the speckle noise. Also, the speckle noise can be removed by applying a non-linear threshold to each frequency in the ultrasound image on the basis of wavelet. However, since the ultrasound image removing the speckle noise according to the conventional methods produces uncomfortable and unnatural feelings, it is not useful for application in a clinical setting. Also, when the ultrasound image removing the speckle noise according to the conventional methods is displayed on a display unit, a problem typically arises in which the boundaries of organs are not clearly displayed.